A sky-blue billboard along Interstate 95 boasts that farther up the road, Jacksonville International Airport has 100 daily departure flights.

True at one time, but not anymore.

Over the past five years, the number of flights departing from Jacksonville International Airport has slumped by 19 percent. In January, the airport averaged 81 daily departures.

The shrinkage stems from an overall contraction in the airline industry during a decade of bankruptcies and mergers. This month, American Airlines and US Airways were the latest to announce they will combine forces.

For travelers, it adds up to fewer flight choices and more expensive tickets. The average price for round-trip flights from Jacksonville International Airport was $359 in the third quarter of 2012, compared to $311 for the same period in 2008, according to U.S. Department of Transportation statistics. That 15 percent increase is the largest of Florida’s seven busiest airports.

The Jacksonville Aviation Authority is trying to get airlines to add flights, such as bringing back nonstop service between Jacksonville and Los Angeles. But that’s tough when airlines are eliminating existing routes.

“We’ve lost some, yes, but not anything out of the ordinary compared to other cities,” said Barbara Halverstadt, manager of development and marketing for the aviation authority. “As consolidation happens, that’s going to be the case.”

“It’s not the kind of place where they’re always trying to fly more and more,” Kaplan said. “They’re trying to get the right mix of putting just enough seats in the market without fares being lower than they have to be, from an airline perspective.”

In some cases, that has meant using smaller 60-passenger planes that don’t have first-class cabins, said Steve Crandall, president of Discount Travel in Jacksonville.

“It’s not only cutting back the number of flights,” he said. “It’s cutting back the size of the aircraft.”

Despite the industry trend, Jacksonville has kept two long-distance, non-stop flights that began the past couple of years.

JetBlue’s non-stop service to San Juan, Puerto Rico, which started in May 2011 with a 100-seat plane, gained enough traction for JetBlue to put a 150-seat jet on that route in October. Southwest Airlines continues to fly nonstop to Denver, a route launched in June 2011.

Southwest is still flying nonstop to Las Vegas, though that service isn’t year-round. The nonstop flights will resume in March.

But Jacksonville lost its only nonstop service to Memphis this year when Delta downsized its hub there. Southwest plans to end nonstop flights between Jacksonville and Birmingham, Ala., in the summer.

The Jacksonville Aviation Authority is supporting JetBlue’s application to the U.S. Department of Transportation for a slot at Ronald Reagan National Airport. Currently, US Airways is the only airline with nonstop flights between Jacksonville and the Washington D.C. airport; United flies nonstop to Dulles International and Southwest to Baltimore-Washington International.

“If all the flights going in and out of Jacksonville were close to capacity, the airlines would react to that and add capacity,” he said. “I don’t think we’re at a choking point in attracting business. If the market grows, I would almost guarantee airlines would do what is necessary to accommodate that market.”

But he said it doesn’t appear the airline industry as a whole is going to change its strategy anytime soon.

In the next month, the authority is going to take down the billboard message that references 100 daily departures, Halverstadt said. The authority hasn’t decided what sign will replace it, but it won’t have a specific number of flights on it.